A buffer is an electronic circuit including a first CMOS inverter and a second CMOS inverter mounted one behind the other, a CMOS inverter being an assembly of a PMOS transistor and an NMOS transistor sharing their gate and drain.
A buffer is therefore an electronic circuit that reproduces the logic state of an input signal on the output.
However, when the input signal changes states, there is a transient period, corresponding to the propagation time, in which the input and the output of the buffer have opposite values. This transient period corresponds to the time needed by the buffer to propagate and transmit, to the output, the change in state of the signal at the input.
So as not to degrade the time performance of an electronic system including a buffer, it is desirable for it to be as fast as possible.
To produce a high-speed buffer, it is known to use a stronger buffer. However, such a solution is limited on the one hand by a propagation time specific to the technology, and, on the other hand, because a larger buffer involves a larger transistor gate capacity and therefore a greater charging time.
As an alternative, it is possible to use transistors with a low threshold voltage. Such transistors are fast, but have higher leakage currents, presenting problems of static consumption.
In addition, to solve these consumption problems, it is known to use transistors with a standard threshold voltage or transistors with a high threshold voltage. Such transistors have lower leakage currents, but are slower.